1. Field of the Invention
The present invention relates to a liquid discharge head comprising a liquid discharge mechanism and a switching circuit, the liquid discharge head being applicable to an apparatus for use in manufacturing a DNA chip, an organic transistor, a color filter or the like, wherein a liquid is discharged by supplying energy to the liquid discharge mechanism to deposit ink droplets on a medium, and more particularly to an ink jet recording head using ink as a liquid, and a method of manufacturing the same.
2. Description of the Related Art
Ink jet recording heads have been extensively studied as liquid discharge heads. In order to obtain high-quality images using an ink jet recording head, it is desirable to discharge ink droplets from respective discharge openings of the ink jet recording head each in an equal volume and always at the same discharge speed. To mention a single example, there has been disclosed in the specification of Japanese Laid-Open Patent Publication (Kokai) No. 6-286149 (US counterpart: U.S. Pat. No. 5,478,606), a method of manufacturing an ink jet recording head, comprising the steps of forming an ink flow path pattern on a substrate with the use of a dissoluble resin, the substrate having ink ejection pressure generating elements thereon using pressure to eject ink, as ink ejection elements, forming on the dissoluble resin layer a coating resin layer, which will serve as ink flow path walls, forming ink ejection outlets in the coating resin layer above the ink ejection pressure generating elements, and dissolving the dissoluble resin layer, by means of which it is possible to set a short distance between the ink ejection pressure generating element and the discharge opening with very high accuracy and precision as well as good reproducibility, and also to achieve high grade recording.
In this manufacturing method, however, a silicon substrate is used as a substrate for the ink jet recording head and the ink flow path walls are made of resin. Therefore, a deformation can easily occur due to a difference in the linear expansion coefficient between the inorganic material (silicon) and the resin, which constitutes a mechanical problem. Furthermore, when the ink flow path walls are made of resin, generally an edge portion of resin tends to be rounded and the edge of the discharge opening is thus rounded. Because of this, there is a problem that ink droplets do not smoothly separate from the discharge opening. Still further, when the ink flow path walls are made of resin, there is a problem that an adequate dimensional precision cannot always be achieved and a satisfactory reliability cannot always be secured since the ink flow path walls may swell and peel off of the base due to the difference in linear expansion coefficient as stated above.
Therefore, as a means of resolving these problems, there has been suggested in the specification of Japanese Laid-Open Patent Publication (Kokai) No. 2000-225708 (US counterpart: U.S. Pat. No. 6,331,259), a method of manufacturing ink jet recording heads comprising the steps of forming a film of a first inorganic material in the form of an ink flow path pattern using a soluble first inorganic material on a substrate having ink-discharge pressure-generating elements formed thereon, forming a film of a second inorganic material becoming ink flow path walls on the film of the first inorganic material using the second inorganic material, forming ink-discharge openings on the film of the second inorganic material above the ink-discharge pressure-generating elements, and eluting the film of the first inorganic material. This method is intended to resolve the above problems that may occur when the ink flow path walls are made of resin, by using an inorganic material for the ink flow path walls.
This method, however, may present a problem of erosion of the inorganic material caused by ink. Particularly, a silicon nitride (SiN) film is used as a material of the ink flow path walls, which material is eroded by alkaline ink. If an ink jet recording head with a SiN film is continuously used, a change may occur in the width of the ink flow path or the diameter of the ink-discharge opening. Furthermore, even if an ink flow path wall of this kind is protected using a plating material of Ni or the like (see, e.g., U.S. Pat. No. 4,438,191), similar erosion still occurs. This problem is not limited to ink, but may also occur depending on the characteristics of liquids used in fabricating a DNA chip, an organic transistor, a color filter or the like.
Therefore, the present invention provides a liquid discharge head in which of a short distance between a liquid discharge element and a discharge opening may be set with extremely high accuracy and precision as well as good reproducibility without any erosion caused by ink or other liquids, and which is also capable of high grade recording, and a method of manufacturing the same.